import airfoil cordinates

michael_stalls

Hi all,

I have airfoil section data in the form of xy coordinates that i would like to import into onshape to use as the basis for a cad model of an aircraft wing. What is the best way to do this? how can i "fix" it so that it can scale but still retain its shape.
thanks
michael

matthew_menard

Can you use a different program to generate a 2d section profile using the x,y data in .dwg format?  If so, you might be able to import those section profiles into a series of planes that have their distances set by the section interval.  I think you should be able to then loft those sections into each other to generate a solid model of the wing.  No idea if that helps, but if not, hopefully somebody else will come along and make a better suggestion.

michael_stalls

thanks,
 i was thinking something along those lines..any suggestions for software that might export dwg or dxf files?

matthew_menard

Draftsight is a free AutoCAD clone that might work for you.

michael_stalls

cheers thanks!

michael_stalls

I tried draftsight and couldn't find out how to import the data and plot it correctly. So i tried another work around instead. I took a screen grab of the airfoil from the cfd mesh and inserted this as a image then used the image as guide for a spline. not ideal but probably good enough as i am using a simple symmetrical airfoil.

I have encountered some problems with this too. The wing i am trying to design is a linearly tapered wing with a constant airfoil section. I made the root airfoil and then tried to copy and paste the root sketch on to the wing tip plane. it does this but pastes the the sketch at the origin when i change the dimension to the tip chord and try to move it to the correct position the spline goes crazy..is there any way you can "fix" the spline so that you can move it around without it deforming?

to get around this i just made a whole new sketch tracing the the airfoil image at the tip...once again not ideal but good enough for now. now i have the root and tip profiles it wont let me create a loft between them. i have used loft with end conditions tangent to profile at both ends. It comes back with an error saying "could not create loft with given information check profile order, guid/profile intersections or end conditions. i have tried inputting things in various different orders and it still wont work. I have used multiple splines to create each airfoil.


because i made top seperate sketches for the root and the tip the points are different for each spline...is this the problem? 

cheers
michael

andrew_troup

@michael_stalls

One way to move sketches without them 'blowing up' in your face is to derive them (unfortunately this can only be done at present to a different part studio) and then move them on arrival.

Check Help for "Derived"

andrew_troup

@michael_stalls

As for end conditions, "tangent" is definitely not what you want, because it makes the loft tangent to a pre-existing extension of the desired surface (sometimes a specially prepared 'tangent skirt', other times it's a boss on the solid part)

You should not generally specify ANY end conditions, if you want a plain tapered loft.